There are many instances where it is necessary or desirable to determine whether an organic fluid contains water as a contaminant. Oftentimes it is also important to determine the actual amount of water present in such organic medium. For example, it may be necessary to determine the amount of water present in fuels (e.g., diesel fuel, aviation fuel, or gasoline) or in lubricants (e.g., oils).
There have previously been proposed a variety of techniques and apparatus for determining the amount of water contained in an organic medium. Such prior techniques have associated disadvantages and limitations.
In U.S. Pat. No. 3,019,342 there is described a technique for detecting trace amounts of water (e.g., parts per million) in hydrocarbon gas, vapor or light liquids. The hydrocarbon to be tested is contacted with a carbide compound capable of releasing a gas such as acetylene. A preferred carbide is said to be calcium carbide which has been tagged with carbon 14. Then the acetylene-containing effluent is passed through a beta-radiation detector which is calibrated to indicate the amount of moisture in the sample. Alternatively, the amount of acetylene produced can be measured volumetrically. When the tagged calcium carbide is used it may be present in a fluidized bed and nitrogen gas may be used to purge the acetylene gas.
U.S. Pat. No. 3,528,775 describes another technique for determining small amounts of moisture contained in petroleum products. The technique involves collecting a small sample of oil to be tested, then extracting it with methanol in a sealed container, separating the methanol phase, and then titrating it to a visual end point with Karl Fischer reagent.
U.S. Pat. No. 3,833,340 describes another technique for determining water content of liquid mixtures. A material (e.g., concentrated sulfuric acid) which interacts with water to generate a measurable exotherm is added to the mixture being tested, after which the resulting temperature increase is measured. The temperature increase must then be compared with a known relationship between temperature increase and water content.
U.S. Pat. No. 3,873,271 describes a method for detecting undissolved water in hydrocarbons. The method involves exposing a sample of hydrocarbon to freshly ground fuchsia dye and calcium carbonate having an average particle size of less than 10 microns and a surface area of 5-8 square meters per gram. If the sample contains more than 10 parts per million water the dye produces a visually perceptible color.
U.S. Pat. No. 3,976,572 describes a device for indicating the presence of water and other contaminants in aircraft fuel. The device is a transparent cylinder which is divided into upper and lower chambers by means of a filter which permits fuel to pass through it but blocks the flow of water and other contaminants.
U.S. Pat. No. 4,089,652 describes a method for detecting water in oil, wherein the oil sample is brought into contact with a reagent which is reactive with water to produce a gas, in a quantity of inert liquid (e.g., kerosine) which is miscible with the oil sample. The inert liquid is also used as the manometric fluid. As the gas is produced the vessel containing all of the ingredients is maintained in a sealed condition and pressure is allowed to build up. Then after the reaction is completed the inert fluid is allowed to escape from the vessel to an ambient pressure vessel where the volume of displaced inert liquid is measured. This technique requires that the inert liquid (i.e., kerosine) be free of water in order to obtain accurate results. Also, since the gas builds up high pressure, some amount of the gas may be lost through small leaks in the cap. After the test is completed the entire quantity of inert fluid is discarded and the vessel must be thoroughly cleaned and dried before further use.
In U.S. Pat. No. 4,151,256 there is described other apparatus for conducting a detection of water in oil. The apparatus includes a container with associated sample cup for oil to be tested. A collector vessel is attached to the container and a delivery tube is provided leading from the bottom of the container to the collection vessel. A valve is present in the delivery tube so that the interior of the container is completely sealed. A liquid such as petroleum hydrocarbon liquid (e.g, kerosine) which is miscible with the test oil is placed in the container. The reagent (i.e., the ingredient which causes gas to be produced when contacted with water) is then added to the liquid while the cover is off the container. A sample of oil to be tested is then placed in the sample cup which in turn is inserted into the container. The cap is then put on the container tightly. The valve in the delivery tube is also closed tightly. Then the apparatus is tilted and shaken so that the oil sample is mixed thoroughly with the inert liquid. Then the container is allowed to sit until the reaction is complete. Finally, the valve is opened and the pressure of any gas produced will drive the inert liquid out of the container through the delivery tube into the collector where it is measured. This apparatus must be very tightly sealed to be able to completely retain all of the gas produced, which creates a great pressure. After the test the entire contents must be disposed of, and the entire apparatus must be thoroughly cleaned and dried before further use.